[英]select the most recent entry
我有下表:
LOCATION_ID, PERSON_ID, DATE
3, 65, 2016-06-03
7, 23, 2016-10-28
3, 23, 2016-08-05
5, 65, 2016-07-14
我想在PL / SQL中建立一个选择查询,以选择每个person_id具有最新 location_id的记录。 对于以上示例,所需结果应为:
LOCATION_ID, PERSON_ID, DATE
5, 65, 2016-07-14
7, 23, 2016-10-28
(日期表示为“ YYYY-MM-DD”)
谢谢!
其他建议是正确的,但是当您使用FIRST_VALUE和LAST_VALUE分析函数时,最可能是最紧凑,最快的解决方案
SELECT DISTINCT
FIRST_VALUE(LOCATION_ID) OVER (PARTITION BY PERSON_ID ORDER BY THE_DATE
ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS LOCATION_ID,
PERSON_ID,
MAX(THE_DATE) OVER (PARTITION BY PERSON_ID) AS LAST_DATE
FROM YOUR_TABLE;
其他人更喜欢
SELECT
MAX(LOCATION_ID) KEEP (DENSE_RANK FIRST ORDER BY DATE) as LOCATION,
PERSON_ID,
MAX(DATE) as LAST_DATE
FROM YOUR_TABLE
GROUP BY PERSON_ID;
这样做是一样的,但是我对这个条款不太熟悉。 参见aggregate_function KEEP
您可以通过将结果按PERSON_ID
分组并选择MAX(DATE)
来首先提取每个人的最新事件。
然后将表本身与这两列相连,以获取LOCATION_ID
SELECT
YOUR_TABLE.LOCATION_ID,
YOUR_TABLE.PERSON_ID,
YOUR_TABLE.DATE
FROM
(SELECT
PERSON_ID, MAX(DATE) AS max_date
FROM
YOUR_TABLE
GROUP BY
PERSON_ID
) AS t1
LEFT JOIN
YOUR_TABLE
ON
YOUR_TABLE.PERSON_ID = t1.PERSON_ID
AND
YOUR_TABLE.DATE = t1.max_date
顺便说一句,您不应对列名使用DATE
类的保留字。
这是用来显示其工作情况的小提琴: http : //sqlfiddle.com/#!9/efdcb/2
@quasoft是正确的。 解决这类GROUP BY
问题的另一种方法(当您要返回的列多于要分组的列时。在这种情况下,您需要返回location_id,person_id。但是只需要按person_id分组)。使用分析函数 。
--schema:
CREATE TABLE my_table
(
location_id NUMBER,
person_id NUMBER,
date_ DATE
);
INSERT ALL
INTO my_table
VALUES (3, 65, To_date('2016-06-03', 'YYYY-MM-DD'))
INTO my_table
VALUES (7, 23, To_date('2016-10-28', 'YYYY-MM-DD'))
INTO my_table
VALUES (3, 23, To_date('2016-08-05', 'YYYY-MM-DD'))
INTO my_table
VALUES (5, 65, To_date('2016-07-14', 'YYYY-MM-DD'))
SELECT *
FROM dual;
--query:
WITH ordered
AS (SELECT location_id,
person_id,
date_,
Row_number()
over (
PARTITION BY person_id
ORDER BY date_ DESC) RN
FROM my_table)
SELECT location_id,
person_id,
date_
FROM ordered
WHERE rn = 1;
查询ordered
排序你行对各组按日期。 主查询在排序后返回每个组的前1个。 因此,在这种情况下,它将返回最后一个(我们由date_desc排序)。
这可能有效!
SELECT * FROM Your_Table A
JOIN (SELECT PERSON_ID,MAX(DATE) as MaxDate FROM Your_Table
GROUP BY PERSON_ID) B
ON A.PERSON_ID = B.PERSON_ID AND A.DATE = B.MaxDate
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